In 1918, with the world at war (WWI), baseball decided
to end its season a month early. On September 1st, Detroit
Tiger outfielder Ty Cobb, baseball's greatest player at
the time, who was scheduled to leave to fight in the war
and thought that he would never return, decided to pitch
in what could have been his last game.

This is the ball that he pitched in that game. He dated
it "Sept. 1 '18" underneath his signature.
Cobb's Tigers played the St. Louis Browns that day and
another great player of the day, first baseman George
Sisler, also ready to go off to war, decided to pitch
against Cobb! He also signed the baseball. (In those
days, they only used one baseball per game, thus the
darkness of the ball). For the record, Sisler hit a
double off of Cobb.